In the early days, the dual in-line package (DIP) method was typically used to solder electronic devices such as connectors to printed circuit boards (PCBs), as briefly described below. To begin with, a PCB is formed with a plurality of plated through holes (PTHs), and the leads of an electronic device are inserted through the corresponding PTHs respectively and hence exposed on the bottom side of the PCB. The bottom side of the PCB is then coated with an appropriate amount of flux to remove the oxidized film on the metal surfaces of the pads on the PCB and of the leads, and to also form a protective film on the aforesaid metal surfaces against further oxidation. After that, the PCB is dipped into the molten solder in a preheated soldering machine in order for the solder to attach to the leads of the electronic device and the PTHs, thereby soldering the electronic device to the PCB.
As electronic products were made increasingly thinner and lighter, and the density of electronic devices on a PCB became higher and higher, the surface-mount technology (SMT) was soon developed and put to use. SMT involves printing the top side of a PCB with solder paste at positions where an electronic device is to be soldered, placing the leads of the electronic device at the solder paste-coated positions, and passing the PCB along with the electronic device through a reflow oven to melt the solder paste and thus solder the electronic device to the PCB. Since SMT does not require forming through holes in a PCB, not only can the PCB be downsized, but also the circuit layout on the PCB can be planned with higher flexibility.
In addition, universal serial bus (USB) ports are nowadays almost indispensable features of electronic products when it comes to data transmission and connection with peripherals, and the demand for “high-speed transmission” has led to a comprehensive upgrade of the USB specifications to USB 3.1. In the meantime, “Type-C connectors” were developed to increase the speed of transmission, the types of signals to be transmitted, and the convenience of hot swapping. One major difference of the Type-C connector structure is its “vertically symmetric configuration”, which allows a user to insert a Type-C connector freely and intuitively into a corresponding socket without having to identify the vertical orientation of the connector first. In order for a Type-C connector to be used with either side up, however, it is necessary that two identical sets of connection terminals be arranged in each such connector. Generally, a Type-C connector can be soldered to a PCB in two ways. The first way, referring to FIG. 1, is to provide a PCB A with two rows of solder pads A1 and A2, wherein all the solder pads in row A1 are SMT-based structures and all the solder pads in row A2 are DIP-based structures. The second way, referring to FIG. 2, is to provide a PCB B with two rows of solder pads B1 and B2, wherein all the solder pads in rows B1 and B2 are SMT-based structures.
The inventor of the present invention, however, found that both ways leave something to be desired in use. More specifically, referring back to FIG. 1, a Type-C connector soldered to the PCB A in the first way tends to produce undesirable near-end crosstalk (simulated NEXT) when the signal being transmitted has a frequency of 4 GHz or 12 GHz. The second way, though effective in ensuring the transmission speed of a Type-C connector soldered to the PCB B in FIG. 2, requires the two sets of connection terminals of the Type-C connector to be placed sequentially on the PCB B such that, once soldered, the connection terminals on the inner side of the connector (especially those close to the center) will be blocked by the connector itself and therefore difficult to check for soldering defects. The issue to be addressed by the present invention is to improve the structure with which a PCB connects with Type-C connectors.